Case hardening



10 to be hardened durin Patented May 22,1928.

PATENT annnnas nnnnmrz, or mum Aachen, 6 1mm.

CASE nannnnme.

.lIo Drawing. Application filed January 25,- 1927, Serial 80. 163,550,311! in Germany February 15, me.

In case-hardening articles of iron or iron allo s there is often desired onl a partial tive mass. However, the protective masses such as kaolin, loam, et cetera used hitherto do not 've surety for completely preventing the di usion of carbon into the portions not the cenientation.

The invention has or its object to avoid .the said drawback by adding a sulphide, for

instance ferrous sulphide, to the known proroved by. 1 numerous tests that a sulphide a ded to the tective masses; It has been said rotective masses securely prevents during t e cementation process any penetration v of carbon into those portions of the articles.

treated which are designed to remain un- 20 hardened.

Having thus described my invention, what I- claim as new and desire to secure I by Letters-Patent is 1. An improved composition of matter used in selective case-hardening, including the additionof ferrous-sulphide to the composition employed to protect portions of the article being case-hardened against such action. 1 v

'2. An improved composition of matter used in selective case-hardening; including the addition of a sulphide to the composition employedtoprotect portions of the article being case-hardened again; such action.

name tothis specification.

- ANDREAS m sn rrz.

'oFFicEi.

In testimony whereof I have signed my 86 

